Why turbines have stages?
What is a steam turbine stage?
- a stage is a pair of rotating and stationary blades (diaphragm, nozzle)- the rotating blades are attached to the rotor
- the stationary blades (stators) are attached to the turbine casing
- steam pressure and temperature drops as it expands and passes to the stages
- steam expansion means increase in volume meaning larger surface area
Why do steam turbines have multiple stages? Why not just use a single stage turbine?
- one stage extracts only a small portion of the available energy from the steam- more stages means more energy extracted
- more energy means more mechanical work at the shaft
- more work means more power (shaft horsepower)
Why turbines need higher vacuum (lower pressure)?
- higher condenser vacuum pressure (lower pressure) means lower exhaust temperature of the steam- higher vacuum pressure means higher thermal efficiency
- higher efficiency means higher power output
- higher efficiency means lesser power losses
Pressure is inversely proportional to Area
HIGH PRESSURE (HP) TURBINE
- steam is at Higher pressure
- steam is at Higher temperature
- steam is at Higher speed
- turbine has Lesser area (lesser diameter)
LOW PRESSURE (LP) TURBINE
- steam is at Lower pressure
- steam is at Lower temperature
- steam is at Lower speed
- turbine has Larger area (larger diameter)
No comments:
Post a Comment